Analytic validation of a competitive polymerase chain reaction assay for measuring Epstein-Barr viral load

Clinical characteristics and prognostic value of pre-retreatment plasma epstein-barr virus DNA in locoregional recurrent nasopharyngeal carcinoma

PURPOSE

To define the clinical characteristics and prognostic value of pre-retreatment plasma Epstein-Barr virus (EBV) DNA, we investigated EBV status in locoregional recurrent nasopharyngeal carcinoma (lrNPC) patients.

METHODS

Between April 2008 and August 2016, the data of patients with nonmetastatic lrNPC were retrospectively reviewed. The survival indexes of patients between different pre-retreatment EBV status groups were compared.

RESULTS

A total of 401 patients with nonmetastatic lrNPC were enrolled, and 197 (49.1%) patients had detectable pre-retreatment plasma EBV DNA. Treatment included radiotherapy alone (n = 37 patients), surgery alone (n = 105), radiotherapy (n = 208), surgery combined with radiotherapy (n = 20), chemotherapy and targeted therapy (n = 31). Median follow-up was 32 months. The 3-year locoregional relapse-free survival (LRRFS), distant metastasis-free survival (DMFS), and overall survival (OS) rates for the entire cohort were 64.8%, 89.4%, and 58.8%, respectively. The estimated 3-year LRRFS, DMFS, and OS rates for the pre EBV-positive group vs the pre EBV-negative group were 54.2% vs 75.0% (P < 0.001), 86.6% vs 91.9% (P = 0.05), 51.6% vs 65.9% (P = 0.01), respectively. Among patients in the clinical stage rI/II, there were 17 patients in the radiotherapy alone group and 49 patients in the surgery alone group. And there was no significant difference in overall survival between radiotherapy and surgery, even among the different pre-EBV statuses (P > 0.05). In terms of long-term toxic and side effects, the incidence of radioactive temporal lobe injury in the radiotherapy group was higher than that in the surgery group (35.3% vs 8.2%, P < 0.001), and no statistically significant difference was found in other long-term toxic and side effects.

CONCLUSIONS

The positive rate of pre-retreatment plasma EBV DNA in lrNPC is lower than primary NPC. The prognosis of EBV DNA negative group is better than positive group. For locally early-stage lrNPC, regardless of EBV DNA status, radiotherapy and surgery are available options and both can achieve better long-term survival.

Detection of Epstein-Barr virus DNA in serum or plasma for nasopharyngeal cancer: a meta-analysis

BACKGROUND

Studies have shown that the plasma or serum cell-free Epstein-Barr virus (EBV) DNA level might be a tumor marker for the diagnosis of nasopharyngeal carcinoma (NPC).

OBJECTIVE

The objective of this study was to evaluate the diagnostic value of the detection of EBV DNA in plasma or serum for NPC.

METHODS

Articles related to the diagnosis of NPC by the detection of EBV DNA in plasma or serum were retrieved from different databases. Sensitivity, specificity, summary receiver operator curves, and likelihood ratios were pooled to assess the diagnostic value of individual diagnostic tests.

RESULTS

Fifteen studies were included in the meta-analysis. The pooled sensitivity and specificity were 89.1% (95% confidence interval [CI], 87.0%-90.9%) and 85.0% (95% CI, 83.0%-86.9%). The subgroup analysis regarding sample type found that the pooled sensitivity and specificity were 91.4% (95% CI, 89.0%-93.4%) and 93.2% (95% CI, 91.2%-95.0%) for the plasma group and 84.4% (95% CI, 79.9%-88.3%) and 76.0% (95% CI, 72.1%-79.6%) for the serum group.

CONCLUSION

The detection of EBV DNA for the diagnosis of NPC has good sensitivity and specificity and might be helpful for the screening of NPC.

Epstein-Barr virus WZhet DNA can induce lytic replication in epithelial cells in vitro, although WZhet is not detectable in many human tissues in vivo

OBJECTIVE

WZhet is a rearranged and partially deleted form of the Epstein-Barr virus (EBV) genome in which the BamH1W region becomes juxtaposed with and activates BZLF1, resulting in constitutive viral replication. We tested whether WZhet induces viral replication in epithelial cells, and we studied its prevalence in a wide range of lesional tissues arising in vivo.

METHODS

A quantitative real-time PCR assay targeting EBV WZhet DNA was developed to measure this recombinant form of the EBV genome.

RESULTS

WZhet DNA was undetectable in any of 324 plasma or paraffin-embedded tissue samples from patients with EBV-associated and EBV-negative disorders. These included specimens from patients with Hodgkin or non-Hodgkin lymphoma, post-transplant lymphoproliferation, nasopharyngeal or gastric adenocarcinoma, and infectious mononucleosis. However, WZhet DNA was detected in vitro in EBV-infected AGS gastric cancer cells. Additionally, transient transfection of infected AGS gastric cancer cells showed that viral replication could be induced by a WZhet plasmid.

CONCLUSION

This is the first evidence that WZhet induces the EBV lytic cycle in an epithelial cell line. Our negative findings in natural settings suggest that WZhet is a defective viral product that thrives in the absence of a host immune system but is rarely present in vivo.

Epstein-Barr Virus (EBV) DNA in Plasma Is Not Encapsidated in Patients With EBV-Related Malignancies

Epstein-Barr Virus (EBV), a ubiquitous gamma herpes virus, infects more than 95% of the human population before adulthood. Life-long persistence, usually without adverse health consequences, relies on a balance between viral latency, viral replication, and host immune response. Patients with EBV-related disease often have high levels of EBV DNA in their plasma. This study addresses whether this circulating, cell-free EBV DNA is encapsidated in virions or exists as naked genomes. First, an assay was developed, combining DNase I and quantitative real-time PCR, to discriminate encapsidated from naked EBV DNA. EBV DNA was almost always naked in the plasma of AIDS-related lymphoma patients (n = 11) and immunosuppressed/posttransplantation patients (n = 8). In contrast, infectious mononucleosis patients (n = 30) often had a mixture of encapsidated and naked EBV DNA. These findings may be important in understanding how viral load relates to disease status and in predicting response to nucleoside analogs and other antiviral therapies.

Measurement of Epstein-Barr virus DNA loads in whole blood and plasma by TaqMan PCR and in peripheral blood lymphocytes by competitive PCR

Epstein-Barr virus (EBV) DNA load values were measured in samples of whole blood (n = 60) and plasma (n = 59) by TaqMan PCR and in samples of peripheral blood lymphocytes (PBLs) (n = 60) by competitive PCR (cPCR). The samples were obtained from 44 transplant recipients. The whole-blood and PBL loads correlated highly (r(2) > 0.900), whereas the plasma and PBL loads correlated poorly (r(2) = 0.512). Testing of whole blood by TaqMan PCR is an acceptable alternative to testing of PBLs by cPCR for quantifying EBV DNA load.

Laboratory markers of tumor burden in nasopharyngeal carcinoma: A comparison of viral load and serologic tests for Epstein-Barr virus

Epstein-Barr virus (EBV) is present within the tumor cells of most cases of nasopharyngeal carcinoma (NPC). Recent studies suggest that tumor burden is proportional to the level of EBV DNA in blood and that rapid blood testing can be used to guide therapeutic intervention. The relative utility of viral load vs. serology has been insufficiently studied. In our study, EBV viral load was measured by quantitative PCR using either real-time or end-point detection systems in serum samples from 124 NPC patients (93 pretreatment, 13 relapsed, 18 in remission) and 40 controls. Serologic titers against EBV early antigen were measured in the same serum samples. EBV DNA was detectable in 64 of 93 untreated NPC patients (69%; mean viral load 11,211 copies/ml), 11 of 13 relapsed NPC patients (85%; mean 53,039 copies/ml) and 0 of 18 remission patients. EBV DNA was detectable in only 1 of 40 non-NPC controls (3%). In 34 instances where paired plasma and serum samples were available for testing, both were effective sample types, and there was no significant difference between end-point and real-time methods for measuring viral load. Early antigen (EA) IgA and IgG titers were elevated in most NPC patients regardless of whether their disease was active or in remission. EBV viral load was more informative than was EA serology for distinguishing remission from relapsed disease. EBV DNA measurement appears to be a noninvasive way to monitor tumor burden after therapy.

Human herpesvirus 8 load in matched serum and plasma samples of patients with AIDS-associated Kaposi's sarcoma

Human herpesvirus 8 (HHV-8) (or Kaposi's sarcoma [KS]-associated herpesvirus) is associated with all forms of KS. HHV-8 DNA load in peripheral blood mononuclear cells (PBMCs) of KS patients has been shown to correlate with the clinical stage of the disease. Studies have been done to assess the HHV-8 viral load in different sample types from KS patients and its clinical relevance. This paper describes the design and evaluation of a quantitative real-time (TaqMan) PCR assay for routine diagnosis of HHV-8 infection. The linear dynamic range was 5 to 5 x 10(6) copies of HHV-8 DNA (r(2) > 0.99). The assay is very sensitive, specific, and easily reproducible (less than 2% variability) and can be used for different clinical samples, such as serum, plasma, and PBMCs. The question of which clinical sample, serum or plasma, is preferable for HHV8 DNA testing was addressed, using this newly developed real-time PCR assay. From 85 patients with diagnosed AIDS-KS, matched plasma and serum samples were collected. Of the 85 patients tested, 35 were positive for HHV-8 DNA in both plasma and serum (41%), 8 were positive in serum but not plasma, and 7 had detectable HHV-8 DNA only in plasma. The HHV-8 load was similar in both plasma and serum, and no significant difference was found. However, more inhibition was seen in the plasma samples with the use of a system quality control, seal herpesvirus type 1. Therefore, our results suggest that serum is the preferred material for HHV-8 load testing, since there is less possible hindrance in the amplification than with plasma.